Archives of Thermodynamics

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Description

The aim of the quarterly journal Archives of Thermodynamics is to
disseminate knowledge between scientists and engineers interested in
thermodynamics and heat transfer and to provide a forum for original
research conducted primarily in Central and Eastern Europe, but also all
over the world. The journal scope of interest encompasses all aspects of
the field, ranging from classical thermodynamics and extended
non-equilibrium thermodynamics, through all modes of heat transfer to
thermodynamic aspects of multiphase flow and combustion. Both
theoretical and applied contributions are welcome. Only original papers
or state-of-art reviews written in English are considered for
publication. All articles are blind peer-reviewed by two independent
reviewers.

Appears since 1980, four issues per year.

Publication funding of this journal is provided by resources of the
Polish Academy of Sciences and The Szewalski Institute of the Fluid-Flow
Machinery of the Polish Academy of Sciences.

ISSN

ISSN 1231-0956, eISSN 2083-6023

Publishers

The Committee on Thermodynamics and Combustion of the Polish Academy of Sciences

Abstract

In the paper presented are experiences from operation of three different
expansion devices for possible implementation in the domestic micro CHP.
These were the modified scroll expander and two designs based on the
variable working chamber volume pneumatic devices. Experiments showed
the superiority of both "pneumatic devices" over the scroll expander,
indicating the possible internal efficiencies in the range of 61 82Such
efficiencies are very attractive, especially at the higher end of that
range. The volume of these devices is much smaller than the scroll
expander which makes it again more suitable for a domestic micro CHP.
Small rotational velocities enable to conclude that connection to
electricity grid will also be simpler in the case of "pneumatic
devices". The "pneumatic devices" under scrutiny here could be an
alternative to the typical vapour turbine in the ORC cycle, which is in
the process of development at the IFFM.

Abstract

The paper analyzes a new concept of integration of combined cycle with
the installation of supplementary firing. The whole system was enclosed
by thermodynamic analysis, which consists of a gas-steam unit with
triple-pressure heat recovery steam generator. The system uses a
determined model of the gas turbine and the assumptions relating to the
construction features of steam-water part were made. The proposed
conception involves building of supplementary firing installation only
on part of the exhaust stream leaving the gas turbine. In the proposed
solution superheater was divided into two sections, one of which was
located on the exhaust gases leaving the installation of supplementary
firing. The paper presents the results of the analyses of which the main
aim was to demonstrate the superiority of the new thermodynamic concept
of the supplementary firing over the classical one. For this purpose a
model of a system was built, in which it was possible to carry out
simulations of the gradual transition from a classically understood
supplementary firing to the supplementary firing completely modified.
For building of a model the GateCycle™ software was used.

Abstract

The article describes the methodology for the determination of ambient
temperature for thermovision measurements. The adopted methodology
consists in the use of the technical blackbody model. Determining the
value of the ambient temperature parameter makes it possible to enhance
the accuracy of temperature measurement of objects exposed to strong
irradiation using a thermovision camera.

Abstract

The analysis of effectiveness of the gradient algorithm for the
two-dimension steady state heat transfer problems is being performed.
The three gradient algorithms - the BCG (biconjugate gradient
algorithm), the BICGSTAB (biconjugate gradient stabilized algorithm),
and the CGS (conjugate gradient squared algorithm) are implemented in a
computer code. Because the first type boundary conditions are imposed,
it is possible to compare the results with the analytical solution.
Computations are carried out for different numerical grid densities.
Therefore it is possible to investigate how the grid density influences
the efficiency of the gradient algorithms. The total computational time,
residual drop and the iteration time for the gradient algorithms are
additionally compared with the performance of the SOR (successive
over-relaxation) method.

Abstract

In the present paper it is proposed to consider the computer cooling
capacity using the thermosyphon loop. A closed thermosyphon loop
consists of combined two heaters and a cooler connected to each other by
tubes. The first heater may be a CPU processor located on the
motherboard of the personal computer. The second heater may be a chip of
a graphic card placed perpendicular to the motherboard of personal
computer. The cooler can be placed above the heaters on the computer
chassis. The thermosyphon cooling system on the use of computer can be
modeled using the rectangular thermosyphon loop with minichannels heated
at the bottom horizontal side and the bottom vertical side and cooled at
the upper vertical side. The riser and a downcomer connect these parts.
A one-dimensional model of two-phase flow and heat transfer in a closed
thermosyphon loop is based on mass, momentum, and energy balances in the
evaporators, rising tube, condenser and the falling tube. The separate
two-phase flow model is used in calculations. A numerical investigation
for the analysis of the mass flux rate and heat transfer coefficient in
the steady state has been accomplished.

Abstract

An analysis of energy efficiency for transcritical compression unit with
CO2 (R744) as the refrigerant has been carried out using empirical
operating characteristics for the two-phase ejector. The first stage of
the refrigerant compression is carried out in the ejector. The criterion
adopted for the estimation of energy efficiency for the cycle is the
coefficient of performance COP. The analysis is performed for the heat
pump and refrigeration systems. The results of COP for the systems with
the ejector has been compared with the COPL values for the single stage
Linde cycle.

Abstract

Thermodynamic analysis of car air cooler is presented in this paper.
Typical refrigerator cycles are studied. The first: with uncontrolled
orifice and non controlled compressor and the second one with the
thermostatic controlled expansion valve and externally controlled
compressor. The influence of the refrigerant decrease and the change of
the air temperature which gets to exchangers on the refrigeration
efficiency of the system; was analysed. Also, its effectiveness and the
power required to drive the compressor were investigated. The impact of
improper refrigerant charge on the performance of air conditioning
systems was also checked.

Abstract

Szargut proposed the algorithm for determination of the influence of
irreversibility of components of thermal process on the emission of CO2
[6]. In the presented paper, basing on Szargut's proposal, the example
of analysis of influence of operational parameters of coal fired power
plant on the local increase of CO2 emission is presented. The influence
of operational parameters on the local exergy losses appearing in
components of investigated power plant are simulating making use of the
semi-empirical model of power plant.

Abstract

In the paper a heating system with a vapour compressor heat pump and
vertical U-tube ground heat exchanger for small residential house is
considered. A mathematical model of the system: heated object - vapour
compressor heat pump - ground heat exchanger is presented shortly. The
system investigated is equipped, apart from the heat pump, with the
additional conventional source of heat. The processes taking place in
the analyzed system are of unsteady character. The model consists of
three elements; the first containing the calculation model of the space
to be heated, the second - the vertical U-tube ground heat exchanger
with the adjoining area of the ground. The equations for the elements of
vapour compressor heat pump form the third element of the general model.
The period of one heating season is taken into consideration. The
results of calculations for two variants of the ground heat exchanger
are presented and compared. These results concern variable in time
parameters at particular points of the system and energy consumption
during the heating season. This paper presents the mutual influence of
the ground heat exchanger subsystem, elements of vapour compressor heat
pump and heated space.

Abstract

The present work is devoted to the problem of utilization of the waste
heat contained in the exhaust gases having the temperature of 350 °C.
Conversion of the waste heat into electricity using a power plant
working with organic fluid cycles is considered. Three Organic Rankine
Cycle (ORC) power plant solutions are analysed and compared: a solution
with the basic, single thermodynamic conversion cycle, one with internal
heat recuperation and one with external heat recuperation. It results
from the analysis that it is the proper choice of the working fluid
evaporation temperature that fundamentally affects the maximum of the
ORC plant output power. Application of the internal heat recuperation in
the plant basic cycle results in the output power increase of approx.
5%. Addition of the external heat recuperation to the plant basic cycle,
in the form of a secondary supercritical ORC power cycle can rise the
output power by approx. 2%.

Abstract

Heat pipes, as passive elements show a high level of reliability when
taking heat away and they can take away heat flows having a
significantly higher density than systems with forced convection. A heat
pipe is a hermetically closed duct, filled with working fluid. Transport
of heat in heat pipes is procured by the change of state of the working
fluid from liquid state to steam and vice versa and depends on the
hydrodynamic and heat processes in the pipe. This study have been
focused on observing the impact these processes have on the heat
process, the transport of heat within the heat pipe with the help of
thermovision. The experiment is oriented at scanning the changes in the
surface temperatures of the basic structural types of capillary heat
pipes in vertical position.

Abstract

The work deals with experimental and numerical thermodynamic analyses of
cross-flow finned tube heat exchangers of the gas-liquid type. The aim
of the work is to determine an impact of the gas non-uniform inlet on
the heat exchangers performance. The measurements have been carried out
on a special testing rig and own numerical code has been used for
numerical simulations. Analysis of the experimental and numerical
results has shown that the range of the non-uniform air inlet to the
considered heat exchangers may be significant and it can significantly
affect the heat exchanger efficiency.

Instructions for authors

Archives of Thermodynamics publishes original papers which have not previously appeared in other journals. The language of the papers is English. No paper should exceed the length of 25 pages. All pages should be numbered. The plan and form of the papers should be as follows:

1. The heading should specify the title (as short as possible), author, his/her complete affiliation, town, zip code, country and e-mail. Please show the corresponding author. The heading should be followed by Abstract of maximum 15 typewritten lines.

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u – velocity, m/s

v – specific volume, m/kg

etc.

The list should begin with Latin symbols in alphabetical order followed by Greek symbols also in alphabetical order and with a separate heading. Subscripts and superscripts should follow Greek symbols and should be identified with separate headings. Physical quantities should expressed in SI units.

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